It has been found that, under certain conditions, it may be difficult to ignite a combustible gas mixture, for example a gas mixture comprising hydrogen and air. This is particularly the case when the combustible gas mixtures are under high pressure.
An example which may be mentioned in this connection is the hydrogenating gasification of solid carbon. It is necessary for the hydrogen which is used as the gasification agent to be raised to a temperature which is suitable for gasification, and which may be 900.degree. C. for example depending on the nature of the coal to be gasified. Conventional heating means, for example heat exchangers, are not normally sufficient to achieve such a temperature. Consequently, a part of the hydrogen must be burnt in order to reach the required temperature level.
Previously proposed methods of igniting such a gas mixture have been found to be unsatisfactory from the point of view of reliability, in particular in regard to safety requirements. If for example hydrogen, methane, heating or fuel gas or the like are mixed, individually or in mixture with each other, with an oxygen-bearing gas such as air, in most practical cases it is necessary to ensure that the reaction between the constituents of the mixture and therefore combustion occurs at the location of the mixing operation, under controllable conditions, as otherwise there is the danger that the combustible mixture may undergo combustion in a manner which is uncontrolled in respect of time and/or location and/or amount and/or speed, as by exploding.